If you ask me, I say Bard to rotation along with Doubront, although at the same time, I would be just fine with a guy like Aaron Cook holding down the 4th slot if he can manage a 4.1-4.2 ERA only because a bullpen with Bailey, Bard, Aceves, Melancon, Padilla (until Rich Hill), Morales, and Albers seems very, very strong.
In terms of Iglesias - Put him at SS all day long. Every single day. The upgrade that Aviles will bring offensively isn't nearly as significant as the upgrade that Iggy brings defensively, and if there is any team in baseball that needs extremely strong defense up the middle, it's the Red Sox. With Pedroia/Iglesias/Ellsbury, I don't think there would be a team in baseball with stronger up-the-middle D. No telling how many hits that could save, which equates to runs saved, which equates to more innings, and thus less innings for our bullpen.
Finally - Lavarnway. I never understood the Shoppach signing. Made zero sense to me. We have a guy in Lavarnway who started game 162 last season, the absolute most important game of the entire season. Now our FO is saying he needs more seasoning? Come on, that's pretty ridiculous.
Cook or Bard as #4 man, Doubront as #5 man. Lavarnway and Salty splitting duties as C. Iglesias as everyday SS.